A covering material to be applied to a skin defect as an artificial skin is called a wound covering material. A pig skin, chitin and so on have already been developed for such a wound cover. These materials, however, have drawbacks in that a new skin developing under the artificial skin may be removed as the artificial skin is being removed. Further, there has recently been developed a wound covering material referred to as "Dioactive CGF" and this wound covering material is less likely to remove the new skin developing under the artificial skin, upon removal of the wound covering material. This wound covering material, however, is said to be slower in the speed of forming a new skin below, as compared to a pig skin.